The present invention relates to a head integrated circuit (IC), a head amplifier circuit, a head suspension assembly, and a magnetic disk drive for avoiding electrostatic breakdown of a magnetic head.
With conventional magnetic disk drives having built-in head suspension assemblies (HSA) each including a suspension on which a head is mounted, it is a standard practice to mount a head amplifier circuit including a read amplifier circuit which amplifies a signal read by the head from a magnetic recording medium, and a write driver circuit which allows the head to write data onto the magnetic recording medium by reversing a direction of current flow to the head, on a flexible printed circuit board (FPC) as a cabling member for interconnections.
The FPC (hereinafter referred to as the main FPC) is formed on top with a pattern of conductive interconnections connected with input/output terminals of the head amplifier circuit. On the opposite side of the interconnections to the head amplifier circuit are formed connection pads which correspond in number to head suspension assemblies (HSAs) used.
To each HSA is fixed a relay FPC which connects the electrodes of the corresponding head attached to its end with a preamplifier circuit through the main FPC. The relay FPC is formed with a pattern of interconnections which are connected at its one end with the electrodes of the corresponding head. The other end of the relay FPC forms a soldering portion consisting of electrode pads connected with the pattern of interconnections. The relay FPC is electrically and mechanically connected with the main FPC by soldering together each electrode pad of the relay FPC and a corresponding one of the connection pads of the main FPC.
Since the FPC has excellent flexibility, the movement of the head along the surface of a magnetic recording medium does never adversely affect the state of connection of the head with the head amplifier through the soldering portion.
As one of means for implementing high-density recording, a so-called combined separate type of magnetic head has recently been used in magnetic disk drives, which uses a magnetoresistive (MR) element that provides high reproduced output as a reproduction head and a thin-film head as a recording head. This type of head is called MR head.
The MR element in the MR head, while providing high reproduced output, has a drawback of being easy to suffer breakdown (electrostatic breakdown) due to electrostatic discharge (ESD). For this reason, a head amplifier circuit has also been developed recently which is equipped with a protection circuit for protecting the MR head from electrostatic breakdown due to ESD.
However, the provision of the MR protection circuit in the head amplifier does not always avoid the electrostatic breakdown of the MR head.
The inventors have found that the breakdown is easy to occur at the time of assembly work of incorporating the HSAs into the drive unit and that the breakdown is caused by ESD that occurs in the vicinity of the soldering portion of the relay FPC through a worker who is soldering together the relay FPC connected with the MR head and the main FPC on which the head amplifier is mounted. In such a case, the MR protection circuit, even if it is provided in the head amplifier circuit, does not function effectively against the ESD occurring in the vicinity of the soldering portion and the ESD directly affects the head. Thus, it is required to prevent effectively the MR head from suffering electrostatic breakdown due to ESD, particularly in the assembly process.
With increase in recording density, band limitation due to noise that occurs in interconnections between the head and the read amplifier and a degradation of the write characteristic due to inductance associated with interconnections between the head and the write driver circuit have become serious problems. It is required to solve these problems.
Accordingly, it is an object of the present invention to provide a head IC, a head amplifier circuit, a head suspension assembly, and a magnetic disk drive which are capable of avoiding electrostatic breakdown of a magnetic head due to, e.g., the occurrence of electrostatic discharge during the assembly process of incorporating the head suspension assembly into the magnetic disk drive.
It is another object of the present invention to provide a head IC, a head amplifier circuit, a head suspension assembly, and a magnetic disk drive which are capable of minimizing the noise leaped in the interconnections between a magnetic head and a read amplifier circuit.
It is still another object of the present invention to provide a head IC, a head amplifier circuit, a head suspension assembly, and a magnetic disk drive which are capable of solving the problem of a degradation of the write characteristic due to inductance associated with interconnections between a magnetic head and a write driver amplifier circuit to be solved.
According to an aspect of the present invention, there is provided a head suspension assembly comprising a magnetic head constituted by a magnetoresistive element for reading data and a head element for writing data; a slider for holding the magnetic head above a surface of a rotating magnetic recording medium; a suspension for supporting the slider; and a head integrated circuit mounted on the suspension, the head integrated circuit including a built-in protection circuit, electrically connected with the magnetoresistive element, for protecting the magnetoresistive element from electrostatic breakdown.
In the head suspension assembly, the head IC may include at least one of a read amplifier circuit for amplifying a read signal read by the magnetoresistive element from the magnetic recording medium and a write driver circuit for supplying the writing head element with a write current corresponding to a write data signal.
According to another aspect of the present invention, there is provided a head amplifier circuit for use in a magnetic disk drive including a head suspension assembly having a magnetic head constituted by a magnetoresistive element for reading data and a head element for writing data, a slider for holding the magnetic head above a surface of a rotating magnetic recording medium, and a suspension for supporting the slider, the head amplifier circuit comprising a head IC (Integrated Circuit) mounted on the suspension, the head IC including a built-in protection circuit, electrically connected with the magnetoresistive element, for protecting the magnetoresistive element from electrostatic breakdown; and a control IC for controlling the head IC.
In the head amplifier circuit, the head IC may include at least one of a read amplifier circuit for amplifying a read signal read by the magnetoresistive element from the magnetic recording medium and a write driver circuit for supplying the writing head element with a write current corresponding to a write data signal.
According to still another aspect of the present invention, there is provided a head IC (Integrated Circuit) for use in a magnetic disk drive including a head suspension assembly having a magnetic head constituted by a magnetoresistive element for reading data and a head element for writing data, a slider for holding the magnetic head above a surface of a rotating magnetic recording medium, and a suspension for supporting the slider, the head IC being mounted on the suspension, the head IC comprising first and second MR terminals connected to both ends of the magnetoresistive element; a bias current terminal connected to receive an externally supplied bias current; and a protection circuit, connected with the first and second MR terminals and the bias current terminal, for protecting the magnetoresistive element from electrostatic breakdown.
The head IC may further comprise a read amplifier circuit for amplifying a read signal read by the magnetoresistive element from the magnetic recording medium. The head IC may further comprise an adjust circuit, connected between the protection circuit and a ground or negative power supply terminal, for adjusting an input impedance of the read amplifier circuit. In this case, the adjust circuit may include one of a resistor and a constant current source.
The head IC may further comprise a write driver circuit for supplying the writing head element with a write current corresponding to a write data signal. The head IC may further comprise a write current circuit for setting a value of the write current supplied from the write driver circuit to the writing head element in accordance with an externally supplied voltage signal.
The head IC may further comprise a read amplifier circuit, connected with the protection circuit, for amplifying a read signal read by the magnetoresistive element from the magnetic recording medium; and a write driver circuit for supplying the writing head element with a write current corresponding to a write data signal.
In the head IC, the protection circuit may includes a first switch circuit for connecting/disconnecting one of the first and second MR terminals to/from the bias current terminal; and a second switch circuit for connecting/disconnecting the other of the first and second MR terminals to/from a ground or negative power supply terminal. The protection circuit may include a voltage limiter circuit, connected between the first and second MR terminals, for limiting a voltage between the first and second MR terminals to a constant value or less. Each of the first and second switch circuits-may be placed in a disconnected state while power is not supplied and in a connected state while power is supplied.
The head IC may further comprise a bias current amplifier circuit, connected between the protection circuit and the bias current terminal, for amplifying a bias current supplied from the bias current terminal. In this case, the protection circuit may includes a first switch circuit for connecting/disconnecting one of the first and second MR terminals to/from the bias current amplifier circuit, and a second switch circuit for connecting/disconnecting the other of the first and second MR terminals to/from a ground or negative power supply terminal. The protection circuit may include a voltage limiter circuit, connected between the first and second MR terminals, for limiting a voltage between the first and second MR terminals to a constant value or less.
According to still another aspect of the present invention, there is provided a magnetic disk drive equipped with a head suspension assembly, the head suspension assembly comprising a magnetic head constituted by a magnetoresistive element for reading data and a head element for writing data; a slider for holding the magnetic head above a surface of a rotating magnetic recording medium; a suspension for supporting the slider; and a head integrated circuit mounted on the suspension and including a built-in protection circuit, electrically connected with the magnetoresistive element, for protecting the magnetoresistive element from electrostatic breakdown.
The magnetic disk drive may further comprise a control integrated circuit for forming a head amplifier circuit in combination with the head integrated circuit and controlling the head integrated circuit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.